Apparatus for measuring the particle size range in a suspension

Abstract

The particle size range of a paper pulp suspension is determined by flowing the suspension up a measuring tube having a filter at the bottom thereof. When a plug of suspended material has formed, the inlet of the measuring tube is closed off. A liquid is then fed to a member which forms a gap in the plug of material and passes up through a measured portion of the suspension. The time taken for the liquid to pass through the plug to a given height is indicative of the mean particle size of the suspension.

What is claimed is: 
     
       1. Apparatus for measuring the particle size range in a suspension, comprising a vertical through-flow passage for the suspension, said passage including a space in which a stationary quantity of suspension from the through-flow passage can collect; a measuring tube connected to said space and being provided with a filter which allows liquid through and traps a plug of suspension particles, and a sealing member to cover and uncover the end of said measuring tube at the end by said space; means in said measuring tube to separate a suspension layer of predetermined thickness from said plug in front of the filter thereby producing a gap in front of the layer to permit the passage of liquid under predetermined pressure through the layer and the filter; and means for measuring the flow rate of said liquid through said layer. 
     
     
       2. Apparatus according to claim 1, wherein the filter and the separating means are disposed in the measuring tube in either a vertical or a horizontal position or any position therebetween. 
     
     
       3. Apparatus according to claim 2, wherein the position of the filter and the separating member is adjustable by adjustment means. 
     
     
       4. Apparatus according to claim 1, wherein a liquid supplier is arranged to supply liquid under predetermined pressure to the separating member, said liquid being used both for separating and for passage through said layer. 
     
     
       5. Apparatus according to claim 1, wherein the measuring tube between the filter and its end at said space is so inclined that the measuring tube can only contain suspension if this is subjected to pressure directed against the filter. 
     
     
       6. Apparatus according to claim 5, wherein said end of said measuring tube by the space is provided with an inflow opening, the surface of which is perpendicular to axis of the through-flow passage. 
     
     
       7. Apparatus according to claim 5, wherein said space is formed by a separating or dividing wall in the through-flow passage. 
     
     
       8. Apparatus according to claim 1, 2, 3, 4, 5, 6 or 7, wherein said measuring means comprises three electrodes to measure liquid penetrating through the filter at different levels as a function of time, the liquid flow rate being an indication of mean particle size in said suspension. 
     
     
       9. Apparatus according to claim 8, wherein the measuring tube is connected at the end located on the same side of the filter as the measuring means to a member supplying cleaning medium to the measuring tube so that this is cleaned and ready to receive a fresh quantity of suspension.